1. Field of the Invention
The present invention pertains to antimicrobial compositions suitable for use in the protection of paints, metal working fluids, process water, mineral slurries, leather, inks, carpet backings, asphalt emulsions, adhesives, dispersions and other wet state industrial products from spoilage resulting from the growth of microorganisms, especially bacteria. The antimicrobial composition comprises mixtures of 1,2-benzisothiazolin-3-one and 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin which, in combination, demonstrate synergistic activity in controlling microorganisms and is an especially useful combination in protecting paint.
2. Description of the Background
Substrates of all types and water-containing compositions and formulations, when exposed to common environmental conditions, are prone to attack, spoilage and various kinds of destruction by a variety of species of microorganisms including fungi, yeast, algae, bacteria and protozoa. As a result, there has always been a great need for effective and economical means to protect, for extended periods of time, commercial compositions and formulations from the deterioration and destruction caused by such microorganisms.
Materials which need protection against such microorganisms include, for example, materials such as paints and other coating formulations, surfactants, proteins, starch-based compositions, inks, emulsions and resins, stucco, concrete, stone, wood adhesives, caulking, sealants, leather, and spin finishes. Other important commercial materials that are prone to degradation by microorganisims are polymer dispersions or aqueous latex paints containing polyvinyl alcohol, polyacrylates or vinylpolymers, thickener solutions containing cellulose derivatives, clay and manual suspensions and metal working fluids. All are prone to degradation by the action of objectionable microorganisms which can spoil and significantly impair the usefulness of such compositions. Such degradation may produce, inter alia, changes in pH values, gas formation, discoloration, the formation of objectionable odors, and/or changes in rheological properties.
Antimicrobials are also important during the processing of materials. For example, animal skins are susceptible to attack by microorganisms both prior to and after the tanning process. Prior to the tanning process, bactericides are used in the brine solutions to prevent bacteria from damaging the hide grain. After the tanning process, the so called wet blue hides are subject to fungal attack during storage or transport and fungicides are used to inhibit this fungal growth. Antimicrobials can also be used in the fat liquors and leather finishing products to prevent the growth of bacteria, fungi and yeast.
A great deal of effort has gone into developing a wide variety of materials which, to various degrees, are effective in retarding or preventing the growth of, and the accompanying destruction caused by, such microorganisms in a variety of circumstances. Such antimicrobial compounds included halogenated compounds, organometallic compounds, quaternary ammonium compounds, phenolics, metallic salts, heterocyclic amines, formaldehyde donors, organosulfur compounds and the like.
No single organic antimicrobial compound is able to provide protection against all microorganisms or is suitable for all applications. In addition to such limitations concerning efficacy, other limitations may restrict the usefulness of certain antimicrobials. For example the stability, physical properties, toxicological profile, regulatory considerations, economic considerations or environmental concerns may render a particular ingredient unsuitable for a particular use. There is a need, therefore, to constantly develop new combinations that will offer broad spectrum protection in a variety of applications.
A judicious choice of combinations may provide a way to maximize benefits while at the same time minimize problems. Ideally, a combination wherein the antimicrobial activity is enhanced while the less desirable properties are suppressed can provide an unexpectedly superior product. The task is to find such combinations that will provide protection against a wide variety of problem microorganisms, will not adversely affect the product to be protected, will maintain its integrity for an extended period of time, and will not have any adverse effect on health or the environment.
The antimicrobial 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin has found wide use in a number of applications as an effective broad spectrum antimicrobial preservative. The antimicrobial 1,2-benzisothiazolin-3-one, including salts thereof, have also found wide use in a number of applications as effective broad spectrum antimicrobial preservatives. What has not been known heretofore is that these two bacteriocides provide a strong synergistic effect when used in combination.